package com.hmdp.utils;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.entity.Shop;
import lombok.extern.slf4j.Slf4j;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.time.LocalDateTime;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import java.util.function.Function;

import static com.hmdp.utils.RedisConstants.CACHE_SHOP_KEY;
import static com.hmdp.utils.RedisConstants.LOCK_SHOP_KEY;

@Slf4j
@Component
public class CacheClient {

    private final StringRedisTemplate stringRedisTemplate;

    public CacheClient(StringRedisTemplate stringRedisTemplate) {
        this.stringRedisTemplate = stringRedisTemplate;
    }
    public void set(String key, Object value,Long time, TimeUnit unit){
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(value),time,unit);
    }

    public void setWithLogicalExpire(String key, Object value,Long time, TimeUnit unit){
        RedisData redisData = new RedisData();
        redisData.setData(value);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(unit.toSeconds(time)));
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(redisData));
    }

    public <R,ID> R queryWithPassThrough(String keyPrefix, ID id, Long time, TimeUnit unit,Class<R> type, Function<ID,R> dbFallback){
        String key = keyPrefix +id;
        //先查redis
        String json = stringRedisTemplate.opsForValue().get(key);
        if (StrUtil.isNotBlank(json)) {  //存在,直接返回
            return JSONUtil.toBean(json, type);
        }
        if (json != null) {//不是null，那就只能是空字符串了
            return null;
        }
        //不存在，查数据库
        R r = dbFallback.apply(id);

        if (r == null) {//数据库不存在，返回错误
            //将空值写入redis（防止缓存穿透）
            stringRedisTemplate.opsForValue().set(key,"",RedisConstants.CACHE_NULL_TTL,TimeUnit.MINUTES);
            return null;
        }
        //数据库里存在，写入redis缓存
        this.set(key,r,time,unit);
        return r;
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);
    public <R,ID> R queryWithLogicalExpire(String keyPrefix,ID id,Long time,TimeUnit unit,Class<R> type,Function<ID,R> dbFallback) {
        String key = keyPrefix + id;
        String json = stringRedisTemplate.opsForValue().get(key);
        if (StrUtil.isBlank(json)) {
            return null;
        }
        RedisData redisData = JSONUtil.toBean(json, RedisData.class);
        R r = JSONUtil.toBean((JSONObject) redisData.getData(),type);
        LocalDateTime expireTime = redisData.getExpireTime();
        if(expireTime.isAfter(LocalDateTime.now())){
            return r;
        }
        String lockKey = LOCK_SHOP_KEY+id;
        boolean isLock = tryLock(lockKey);
        if(isLock){
            CACHE_REBUILD_EXECUTOR.submit(()->{
                    try{//重建缓存
                        //先查询数据库
                        R r1 = dbFallback.apply(id);
                        this.setWithLogicalExpire(key,r1,time,unit);
                        //再写缓存
                    }catch (Exception e){
                        throw new RuntimeException(e);
                    }finally {
                        unlock(lockKey);
                    }
            });
        }
        return r;
    }


    private boolean tryLock(String key){
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }
    private void unlock(String key){
        stringRedisTemplate.delete(key);
    }
}
